EP0392732A1

EP0392732A1 - Automatic mechanical transmission start control system

Info

Publication number: EP0392732A1
Application number: EP90303601A
Authority: EP
Inventors: Eugene Ralph Braun
Original assignee: Eaton Corp
Current assignee: Eaton Corp
Priority date: 1989-04-14
Filing date: 1990-04-04
Publication date: 1990-10-17
Also published as: US5097724A

Abstract

In a start control system a central processing unit (10) processes signals indicative of throttle pedal position (26), engine speed (20), transmission input speed (14), and transmission output speed (16) and controls either or both the degree of clutch (6) and brake (24) engagement to provide smooth start up when vehicle speed is less than a predetermined value.

Description

INTRODUCTION:

This invention relates generally to a vehicular automatic transmission control system effective to provide a substantially smooth start-up from a stopped or virtually stopped condition and more particularly to such control system including means for instructing the vehicle brakes to assume a predetermined partially engaged condition in combination with means for instructing a frictional coupling to establish a predetermined partially engaged condition between the transmission and the vehicle engine.

BACKGROUND OF THE INVENTION:

A variety of approaches have been taken over the years to prevent a vehicle having an automatic transmission from creeping when in a stopped condition with the transmission in neutral with the engine running and to provide a smooth start-up from a stopped or virtually stopped condition.
A system that employs a mechanism for raising the idling speed of the engine during warm-up and also for automatically disengaging or partially disengaging the clutch when the brakes are applied at the lowest speed is described in U.S. Patent 4,105,101, the disclosure of which is incorporated herein by reference.
A somewhat similar concept is disclosed in U.S. Patent 4,194,608, of which the disclosure is incorporated herein by reference, teaches a means by which to adjust throttle position when the clutch assembly uncouples the transmission from the engine.
U.S. Patent 4,513,638, the disclosure of which is incorporated herein by reference, discloses a system that prevents the clutch from coupling the transmission to the engine when the throttle valve is in idle and the gear shift is moved from neutral to another position.
A system for reducing torque applied to an automatic transmission when the engine is idling is disclosed in U.S. Patent 4,514,811, the disclosure of which is incorporated herein by reference.
Other examples of systems for controlling creep and/or enhancing smoothness in start-up of vehicles having automatic transmissions are disclosed in U.S. Patents 4,579,202; 4,618,043; 4,698,763; 4,711,141; and 4,714,144, the disclosures of all of which are incorporated herein by reference.
Although the control systems disclosed in the above-described references may have their particular advantages, they characteristically employ means for automatically disengaging or partially engaging the clutch often in combination with some type of fuel control to maintain a desired idling speed and, although the previously described mechanism in U.S. Patent 4,105,101 utilizes partial disengagement of the vehicle brakes as a smoothing function, such is done only in conjunction with idle speed control and does not include the advantage of partial clutch engagement.

SUMMARY OF THE INVENTION:

It has been discovered that a balancing between the degree of clutch engagement and the amount of force applied to the brakes in combination with automatic fuel adjustment operates to great advantage in controlling creep and providing smooth start-up of vehicles employing automatic transmissions that has long been recognized by those skilled in the art.
Accordingly, it is an object of this invention to provide a system for controlling creep and providing smooth start-up for vehicles having automatic transmissions.
It is another object of this invention to provide a vehicular automatic transmission control system that controls degree of brake and clutch engagement in combination with engine idle speed adjustment to control creep and enhance smoothness of start-up.
It is still another object of this invention to provide a vehicular automatic transmission control system that balances the degree of clutch engagement against the degree of braking in combination with automatic engine idle speed adjustment to control creep and enhance smoothness of start-up.
It is yet another object of this invention to provide a vehicular automatic transmission control system that determines the amount of clutch engagement for starting smoothness by causing the engine speed to drip a predetermined amount with the brakes automatically applied or maintained.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIGURE 1 is a schematic illustration of the components and interconnections of the automatic mechanical transmission control system of the invention; and
FIGURES 2 & 3 are respective symbolic illustrations of alternate embodiments of the automatic mechanical transmission control system of the invention in flow chart form.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS:

In Figure 1, a vehicular engine 2, such as an internal combustion gasoline or diesel engine, is operative to drive an output shaft 17 of an automatic mechanical transmission 4 which is selectively coupled to engine 2 by means of frictional coupling or clutch 6.
Output shaft 17 is operatively connected to the vehicle drive wheels by means of an axle differential or the like causing the wheels to rotate and move the vehicle in response to rotation of output shaft 17.
Output shaft 17 is caused to rotate when transmission 4 is coupled to engine 2 by clutch 6. The rotational speed and direction in which output shaft 17 rotates is governed by the particular change gear ratio of transmission 4 engaged at the time.
The change gear ratio is selected by an operator by positioning a knob or the like, not shown, at R (reverse) or at progressively increasing drive ratios denoted as D_L, D₁, and D or in N (neutral) when so selected not to be in gear.
Generally, the control system of the invention is operative to prevent the vehicle from creeping when the transmission is in neutral and the engine is idling by ensuring that frictional coupling or clutch 6 is in a fully disengaged condition. Additionally, the control system of the invention is operative to ensure smooth starting conditions at vehicle speeds less then a predetermined value K hereinafter described with respect to Figures 2 and 3. The automatic partial engagement of clutch 6 with the automatic engagement of the brakes takes the backlash out of the driveline to contribute to the smoothness of the start. Additionally, the automatic release of the brakes at a predetermined rate allows for a smooth vehicle start.
The control system of the invention includes a central processing unit 10 operative to provide output signals to brake control or actuation means 24 and to effect gear ratio selections in transmission 14 as well as adjust engine fuel control 22 in addition to controlling operation of clutch 6.
In order to provide the necessary output signals, central processing unit 10 receives input signals from transmission output speed sensor 16, and from brake control 24, and from transmission input shaft speed sensor 14, as well as from engine speed sensor 20, and engine fuel control 22, and optionally from throttle foot pedal position sensor 26.
Central processing unit 10 is operative to receive and process the input signals to provide output signals operative to coordinate idle speed adjustment and the degree of brake and clutch engagement required to minimize creep and provide smooth operation at low speed.
The particular sensor employed for providing the input signals to processing unit 10 and the mechanism for controlling the degree of clutch and brake engagement are well known in the art and are therefore not described in detail herein.
Automatic and semi-automatic transmission systems of the type illustrated in Figure 1 maybe seen in greater detail by reference to U.S. Patent Nos. 4,361,060; 4,595,986; 4,722,248 and 4,648,290, the disclosures of which are incorporated herein by reference.
The logic path or pattern for the control system of the invention however uniquely combines parameters heretofor not brought together in toto and is therefore described herein in detail with respect to Figures 2 and 3.
Figure 2 illustrates the logic pattern by which processing unit 10 processes various input signals to provide the output signals required to minimize creep and provide smooth driving conditions at low speeds.
Start-up control 28 is governed first in operation or step 30 by determining if vehicle speed is less than a predetermined value K which, for example, may be 3 miles per hour.
If the answer is no, then vehicle speed is above the predetermined threshold value at which the system of the invention is operative to control.
If the answer is yes, it is determined in step 32 whether throttle foot pedal position 26 is in an idle position. If yes, it is determined in step 34 whether the transmission is in neutral. If yes, unit 10 provides an output signal operative to cause the friction coupling or clutch 6 to assume a fully disengaged condition.
In the event it is determined in step 34 that the transmission is not in neutral, unit 10 provides an output signal operative to cause the brake actuation means to apply the brakes lightly which may be described as causing the brakes to assume a predetermined partially engaged condition.
Additionally, unit 10 provides an output signal effective to cause the clutch to engage with a light drag or otherwise described as causing the clutch to assume a predetermined partially engaged condition that is adapted to smooth travel at speeds below threshold value K by unit 10 additionally providing an output signal that is effective to adjust engine fuel to hold idle speed at a predetermined value and then recycle into the logic program as indicated by the arrow presuming that the vehicle speed remains below threshold value K.
In some of the cases, the amount of clutch engagement is determinable by the amount of engine speed drop or by the degree of engine fuel adjustment. The clutch engagement can thus be stopped when the engine speed decreases a predetermined amount. Alternately, the clutch engagement can be stopped when the engine fuel adjustment to maintain a pretetermined engine speed has reached a predetermined value.
If the engine has an idle speed governor, fuel will be adjusted to maintain idle speed and operation or step 42 would not be required in the system.
In the event it is determined in step 32 that the throttle foot pedal is not in an idle position, then it is determined in step 44 whether the transmission is in neutral and, if yes, the cycle is restarted at reference numeral 28 as shown by the arrow or, if not, unit 10 provides an output signal that, in step 46, is effective to cause the brake actuation means to release or disengage the brakes slowly or, as may be otherwise described, as at a predetermined rate after which the start control system will return to the automatic transmission clutch engagement routine of which many are known to those skilled in the art such as the routine disclosed in U.S. Patent 4,081,065, the disclosure of which is incorporated herein by reference.
Thus, the control system of the invention operates to (1) fully disengage the clutch when vehicle speed is below a threshold value K and the throttle is at idle and the transmission is in neutral and; (2) apply the brakes and clutch lightly and adjust idle speed to provide smooth operation when vehicle speed is less than predetermined threshold value K and the throttle is initially in an idle position and the transmission is not in neutral and; (3) to release the brakes slowly at a predetermined rate when applied and the vehicle speed is less than predetermined threshold value K and the throttle is not at idle and the transmission is not in neutral and then return to the clutch engagement routine as shown in Figure 2.
An alternative system is provided by omitting the clutch lightly applied condition at step 40 in favor of the condition that whenever the throttle foot pedal is moved from idle, the clutch is lightly applied and the brakes released slowly.Another embodiment of the control system of the invention is shown in Figure 3, which comparison will show operates in essentially the same manner as the system of Figure 2 except that instead of the sequence of steps 38, 40 and 42, the clutch is again engaged with light drag in step 40 and a determination is made in step 48 as to whether the brakes are in an engaged condition and, if yes, unit 10 provides an output signal effective to cause the brake actuation means to hold the brakes in a lightly applied condition and, if not, to return to the logic program as shown by the arrow in Figure 3 unless the vehicle speed has climbed above the predetermined value K which, as previously described, is a speed preferably below about 3 miles per hour.
Although the present invention has been set forth with a certain degree of particularity, it is understood that various modifications are possible without departing from the spirit and scope of the invention as hereinafter claimed.

Claims

1. An automatic mechanical transmission (4) start control system for vehicles having a throttle controlled engine (2) , said transmission (4) having a plurality of gear ratio combinations selectively engageable between a transmission output shaft (17) and a transmission input shaft operatively connected to the engine (2) by means of a selectively engageable and disengageable friction coupling (6), said system including automatic friction coupling actuating means (18), automatic vehicle brake actuating means (24), operator actuated throttle control means (26), operator positionable change gear selector means (8) including a neutral position and positions in which said gear ratio combinations are selectively engaged, and an information processing unit (10) having means for receiving a plurality of signals including; (1) an input signal (20) indicative of the position of said throttle control means or of the amount of fuel supplied to the engine (2); (2) an input signal (16) indicative of vehicle speed; and (3) an input signal (12) indicative of the gear ratio combination selected, said processing unit (10) including means for processing said input signals and providing an output signal therefrom such that, when the vehicle speed signal is less than a predetermined value and the throttle control means is in an engine idle position, said output signal is effective to (i) instruct the friction coupling to assume a fully disengaged condition when the operator change gear selector means is in the neutral position and (ii) instruct the brake actuating means to cause the brakes to assume a predetermined partially engaged condition and instruct the friction coupling actuation means to cause the friction coupling to assume a predetermined partially engaged condition when the operator change gear selector means is not in a neutral position.

2. An automatic mechanical transmission (4) start control system for vehicles having a throttle controlled engine (2), said transmission (4) having a plurality of gear ratio combinations selectively engageable between a transmission output shaft (17) and a transmission input shaft operatively connected to the engine (2) by means of a selectively engageable and disengageable friction coupling (6), said system including automatic friction coupling actuating means (18), automatic vehicle brake actuating means (24), operator actuated throttle control means (26), operator positionable change gear selector means (8) including a neutral position and positions in which said gear ratio combinations are selectively engaged, and an information processing unit (10) having means for receiving a plurality of signals including; (1) an input signal (20) indicative of the position of said throttle control means or of the amount of fuel supplied to the engine (2); (2) an input signal (16) indicative of vehicle speed; and (3) an input signal (12) indicative of the gear ratio combination selected, said processing unit (10) including means for processing said input signals and providing an output signal therefrom such that, when the vehicle speed signal is less than a predetermined value and the throttle control means is in an engine idle position, said output signal is effective to (i) instruct the friction coupling to assume a fully disengaged condition when the operator change gear selector means is in the neutral position and (ii) after the operator has applied the brakes to instruct the brake actuating means to maintain the brakes applied at predetermined partially engaged condition and instruct the friction coupling actuation means to cause the friction coupling to assume a predetermined partially engaged condition when the operator change gear selector means is not in a neutral position.

3. The system of claim 1 or 2, wherein the processing unit is further operable to provide an output signal therefrom such that when the vehicle speed input signal (16) is below a predetermined value and the throttle control means (26) is not in an engine idle position and the change gear selector means (8) is not in the neutral position, said output signal is effective to instruct the brake actuation means (24) to disengage the brakes at a predetermined rate.

4. The system of claim 1 or 2 wherein said output signal is operative to instruct the engine fuel control means (22) to adjust fuel as necessary to hold the engine (2) at a predetermined engine idle speed.

5. The system of claim 3 wherein said output signal is operative to instruct the engine fuel control means (22) to adjust fuel as necessary to hold the engine (2) at a predetermined engine idle speed.

6. An automatic mechanical transmission (4) start control system for vehicles having a throttle controlled engine (2), said transmission having a plurality of gear ratio combinations selectively engageable between a transmission output shaft (17) and a transmission input shaft operatively connected to the engine (2) by means of a selectively engageable and disengageable friction coupling (16), said system including automatic friction coupling actuating means, automatic vehicle brake actuating means (18), operator actuated throttle control means (26), operator positionable change gear selector means (8) including a neutral position and positions in which said gear ratio combinations are selectively engaged, and an information processing unit (10) having means for receiving a plurality of signals including; (1) an input signal (20) indicative of the position of said throttle control means or of the amount of fuel supplied to the engine; (2) an input signal (16) indicative of vehicle speed; and (3) an input signal (12) indicative of the gear ratio combination selected, said processing unit (10) including means for processing said input signals and providing an output signal therefrom such that, when the vehicle speed signal (20) is less than a predetermined value, said start control system is operative such that, when the transmission (4) is not in neutral and the throttle is at idle, the friction coupling and the brakes are respectively automatically engaged a predetermined amount.

7. An automatic mechanical transmission (4) start control system for vehicles having a throttle controlled engine (2), said transmission (4) having a plurality of gear ratio combinations selectively engageable between a transmission output shaft (17) and a transmission input shaft operatively connected to the engine by means of a selectively engageable and disengageable friction coupling (6), said system including automatic friction coupling actuating means (18), automatic vehicle brake actuating means (24), operator actuated throttle control means (26), operator positionable change gear selector means (8) including a neutral position and positions in which said gear ratio combinations are selectively engaged, and an information processing unit (10) having means for receiving a plurality of signals including; (1) an input signal (20) indicative of the position of said throttle control means or of the amount of fuel supplied to the engine; (2) an input signal indicative of vehicle speed (16); and (3) an input signal (12) indicative of the gear ratio combination selected, said processing unit (10) including means for processing said input signals and providing an output signal therefrom such that, when the vehicle speed signal (16) is less than a predetermined value, said start control system is operative such that, when the transmission (4) is not in neutral and the throttle is at idle, the brakes are automatically engaged a predetermined amount and, when the throttle is moved from the idle position, the friction coupling (6) is engaged a predetermined amount and the brakes are automatically released at a predetermined rate.

8. An automatic mechanical transmission (4) start control system for vehicles having a throttle controlled engine (2), said transmission (4) having a plurality of gear ratio combinations selectively engageable between a transmission output shaft (17) and a transmission input shaft operatively connected to the engine (2) by means of a selectively engageable and disengageable friction coupling, said system including automatic friction coupling (6) actuating means (18), automatic vehicle brake actuating means (24), operator actuated throttle control means (26), operator positionable change gear selector means (8) including a neutral position and positions in which said gear ratio combinations are selectively engaged, and an information processing unit (10) having means for receiving a plurality of signals including; (1) an input signal (20) indicative of the position of said throttle control means or of the amount of fuel supplied to the engine; (2) an input signal (16) indicative of vehicle speed; and (3) an input signal (12) indicative of the gear ratio combination selected, said processing unit (10) including means for processing said input signals and providing an output signal therefrom such that, when the vehicle speed signal is less than a predetermined value, said start control system is operative such that, when the transmission (4) is not in neutral and the throttle is at idle, the friction coupling (6) is automatically engaged a predetermined amount and the brakes, if applied by the operator, will be maintained automatically even when released by the operator.

9. An automatic mechanical transmission (4) start control system for vehicles having a throttle controlled engine (2), said transmission (4) having a plurality of gear ratio combinations selectively engageable between a transmission output shaft (17) and a transmission input shaft operatively connected to the engine (2) by means of a selectively engageable and disengageable friction coupling (6), said system including automatic friction coupling actuating means (16), automatic vehicle brake actuating means, operator actuated throttle control means (26), operator positionable change gear selector means (8) including a neutral position and positions in which said gear ratio combinations are selectively engaged, and an information processing unit (10) having means for receiving a plurality of signals including; (1) an input signal (20) indicative of the position of said throttle control means or of the amount of fuel supplied to the engine (2); (2) an input signal (16) indicative of vehicle speed; and (3) an input signal (12) indicative of the gear ratio combination selected, said processing unit (10) including means for processing said input signals and providing an output signal therefrom such that, when the vehicle speed signal (16) is less than a predetermined value, said start control system is operative such that, when the transmission (4) is not in neutral and the throttle is at idle, the brakes, if applied by the operator, will be automatically maintained even if released by the operator and, when the throttle is moved from the idle position, the friction coupling (6) is engaged a predetermined amount and the brakes are automatically released at a controlled rate.

10. The system of claim 6 or 8 wherein, when the throttle control means (26) is moved from the idle position, the brakes are automatically released at a controlled rate.

11. The system of claims 6, 7, 8, or 9 wherein, said output signal is operative to instruct the engine fuel control means (22) to adjust fuel as necessary to hold the engine (2) at a predetermined engine idle speed.

12. An automatic mechanical transmission (4) start control system for vehicles having a throttle controlled engine (2), said transmission (4) having a plurality of gear ratio combinations selectively engageable between a transmission output shaft (17) and a transmission input shaft operatively connected to the engine (2) by means of a selectively engageable and disengageable friction coupling, said system including automatic friction coupling (6) actuating means (18), automatic vehicle brake actuating means (24), operator actuated throttle control means (26), operator positionable change gear selector means (8) including a neutral position and positions in which said gear ratio combinations are selectively engaged, and an information processing unit (10) having means for receiving a plurality of signals including; (1) an input signal (20) indicative of the position of said throttle control means or of the amount of fuel supplied to the engine; (2) an input signal (16) indicative of vehicle speed; and (3) an input signal (18) indicative of the gear ratio combination selected, said processing unit (10) including means for processing said input signals (16) and providing an output signal therefrom such that, when the vehicle speed signal is less than a predetermined value, said start control system is operative such that, when the transmission is not in neutral and the throttle is at idle, the brakes are automatically engaged a predetermined amount and the friction coupling (6) is automatically partially engaged an amount effective to cause the engine speed to decrease a predetermined amount.

13. An automatic mechanical transmission (4) start control system for vehicles having a throttle controlled engine (2), said transmission (4) having a plurality of gear ratio combinations selectively engageable between a transmission output shaft (17) and a transmission input shaft operatively connected to the engine (2) by means of a selectively engageable and disengageable friction coupling (6), said system including automatic friction coupling actuating means (18), automatic vehicle brake actuating means (24), operator actuated throttle control means (26), operator positionable change gear selector means (8) including a neutral position and positions in which said gear ratio combinations are selectively engaged, and an information processing unit (10) having means for receiving a plurality of signals including; (1) an input signal (20) indicative of the position of said throttle control means or of the amount of fuel supplied to the engine; (2) an input signal (16) indicative of vehicle speed; and (3) an input signal (12) indicative of the gear ratio combination selected, said processing unit (10) including means for processing said input signals and providing an output signal therefrom such that, when the vehicle speed signal (16) is less than a predetermined value, said start control system operative such that, when the transmission is not in neutral and the throttle is at idle, the brakes are automatically engaged a predetermined amount and, when the throttle is moved from the idle position, the friction coupling (6) is automatically engaged an amount effective to cause the engine speed to decrease a predetermined amount followed by the brakes being automatically released at a predetermined rate.

14. An automatic mechanical transmission (4) start control system for vehicles having a throttle controlled engine (2), said transmission having a plurality of gear ratio combinations selectively engageable between a transmission output shaft (17) and a transmission input shaft operatively connected to the engine by means of a selectively engageable and disengageable friction coupling (6), said system including automatic friction coupling actuating means (18), automatic vehicle brake actuating means (24), operator actuated throttle control means, operator positionable change gear selector means (8) including a neutral position and positions in which said gear ratio combinations are selectively engaged, and an information processing unit (10) having means for receiving a plurality of signals including; (1) an input signal (20) indicative of the position of said throttle control means or of the amount of fuel supplied to the engine; (2) an input signal (16) indicative of vehicle speed; and (3) an input signal (12) indicative of the gear ratio combination selected, said processing unit (10) including means for processing said input signals and providing an output signal therefrom such that, when the vehicle speed signal (16) is less than a predetermined value, said start control system is operative such that, when the transmission (4) is not in neutral and the throttle is at idle, the brakes, if applied by the operator, will be automatically maintained even if released by the operator, and the friction coupling will be automatically engaged an amount effective to cause the engine speed to decrease a predetermined amount.

15. An automatic mechanical transmission (4) start control system for vehicles having a throttle controlled engine (2), said transmission (4) having a plurality of gear ratio combinations selectively engageable between a transmission output shaft and a transmission input shaft (17) operatively connected to the engine by means of a selectively engageable and disengageable friction coupling (6), said system including automatic friction coupling actuating means (18), automatic vehicle brake actuating means (24), operator actuated throttle control means (26), operator positionable change gear selector means (8) including a neutral position and positions in which said gear ratio combinations are selectively engaged, and an information processing unit (10) having means for receiving a plurality of signals including; (1) an input signal (20) indicative of the position of said throttle control means or of the amount of fuel supplied to the engine; (2) an input signal (16) indicative of vehicle speed; and (3) an input signal (12) indicative of the gear ratio combination selected, said processing unit (10) including means for processing said input signals and providing an output signal therefrom such that, when the vehicle speed signal is less than a predetermined value, said start control system operative such that, when the transmission (4) is not in neutral and the throttle is at idle, the brakes, if applied by the operator, will be automatically maintained even if released by the operator and, when the throttle is moved from the idle position, the friction coupling (6) is engaged an amount effective to cause the engine speed to decrease a predetermined amount followed by the brakes being automatically released at a controlled rate.

16. The system is claim 12 or 14 wherein, when the throttle is moved from the idle position, the brakes are automatically released at a controlled rate.

17. The system of claim 12, 13, 14 or 15 wherein, the output signal is operative to instruct the friction coupling control means (18) to stop engaging and to instruct the engine fuel control means (18) to adjust fuel as necessary to hold the engine speed at a predetermined value.

18. The system of claim 6, 7, 8 or 9 wherein, the output signal is operative to instruct the friction coupling actuating means (18) to engage the friction coupling (6) until the engine fuel control means (22) has adjusted the fuel a predetermined amount to maintain a predetermined engine speed and then to stop the engagement of the friction coupling (6).